Modern aircraft typically utilize multiple on-board electrical systems and controls to ensure proper operation of the aircraft. In some examples, one or more of the on-board electrical systems communicate with a pilot, or the cockpit in general, via a single line communication bus. Such systems are referred to herein as single line communication systems.
One environmental risk aircraft are exposed to during flight is the potential of a lightning strike hitting the aircraft. When lightning strikes an aircraft, a surge of electricity passes through the aircraft and any unprotected electrical systems onboard the aircraft. The surge can overload unprotected electrical systems and damage or destroy the unprotected electrical system. This surge of electricity is referred to as a lightning transient surge. In order to protect against these lightning transient surges, aircraft include lightning protection circuits connected to one or more on board electrical systems. The lightning protection circuits shunt the lightning transient surge away from the protected electrical system, and to a neutral power line.
Some existing lightning protection circuits utilize a transient voltage suppression device as a clamping portion of the transient surge protection. Further, in some cases the transient voltage suppression device can enter a short circuit failure mode. While in the short circuit failure mode, the transient voltage suppression device directly connects the single line communication bus to a neutral point causing the communication bus to be unable to communicate with the cockpit. As the single line communication bus cannot communicate with the cockpit, each of the sensors, controllers, and other aircraft components that rely on the communication bus to transmit signals to the cockpit likewise cannot communicate with the cockpit.
In existing single communication line systems, the cockpit is unable to determine whether a communication interruption is due to a failed transient voltage suppression device or a more serious failure in one or more of the systems communicating over the single line communication bus. As a result, a failure of the transient voltage protection device is treated as a “worst case scenario” even when the aircraft components that communicate over the single line communication bus may otherwise be fully operational.